1. Field of the Invention
The subject invention relates to telephone systems, to telephone sets, to telephone set accessories, to methods and apparatus for tapping audio signals at telephone sets, and to methods and apparatus for amplifying, recording, processing or otherwise utilizing telephone audio signals. The term "audio signal" as herein employed is not intended to be limited to signals intended to be heard by a telephone user, but is intended to be broad enough to extend to signals as transmitted over the phone for data processing, facsimile, transcribing, computer operating and similar purposes.
2. Disclosure Statement
The following disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments which may be subsequent in time or priority.
In the evolution of technology, it is a frequently observed fact that certain fields or branches become stagnant because of a pervading inability of otherwise skilled persons throughout the particular field to rise above one or more entrenched prior-art approaches which may have been initially justified against the background of certain equipment, but which became a barrier to progress and were thus unable to keep up with an evoluation of that equipment. The background of the subject invention presents such an instance of prior-art stagnation, as will become apparent in the further course of this disclosure.
By way of background, there are many reasons for deriving or tapping an audio signal from a telephone set. For instance, when calling a person's office, it would frequently be desirable to leave a short personal recorded message with his or her secretary or receptionist. Recording of phone messages at order or sales desks is also generally desirable. Telephone signal amplifiers or speaker phones also require a tapped audio signal for their operation. The wide proliferation of facsimile, transcribing, data processing, computer and similar systems operating via telephone lines and sets also call for an electrical audio signal tapping technique that is superior to the now frequently used acoustical coupling over the handset or to other prior-art methods.
Other examples include emergency phone recording, such as by police stations and fire departments, and law enforcement surveillance and authorized wiretapping.
Many telephone recording or signal tapping systems have been developed in the past. Complexities range from large voice-activated systems, with special date and time logging, to small electronic boxes, typically sold at hobby stores, which plug into the phone line and employ a separate cassette recorder, frequently activated by an ON/OFF switch.
One type of prior-art approach makes the signal tapping connection directly to the telephone line pair. In practice, this entails several disadvantages. For one thing, any recorder or other apparatus connected to the wiretap inevitably will be exposed to the large difference in audio levels occurring when signals are transmitted from a nearby station or via line amplifiers in one instant and from a more remote station in another. In an effort to prevent a weak signal from being masked or lost and a strong signal from being distorted, automatic level control circuitry has been tried. This, however, inevitably increases the cost of the system and precludes the use of a readily available typical cassette recorder, inasmuch as automatic level control circuitry would have to be of considerable sophistication to start with.
Moreover, an audio signal tapping device that operates directly from the phone line inevitably becomes inadequate with the many multi-line or key-button phones increasingly used in offices and businesses where the demand for a speaker phone system, phone message recorder and data transmission generally is strongest.
Tapping approaches which would invade the internal wiring system of the telephone set are also disfavored, not only by the telephone company, but also by public agencies charged with assuring a safe operation of the telephone system. Accordingly, equipment which requires connection inside the telephone set was traditionally reserved to installation by the phone company. In practice, this had the disadvantage of an inherent limitation to the type of equipment which the phone company chose to carry. Equally seriously, use of such equipment typically entailed an extra charge on the monthly phone bill with practically no amortization. Thus, it was and still is not unusual that phone subscriber using equipment that would have been amortized by the monthly extra charge in less than a year, nevertheless had and have to keep paying such charge for years, as long as they are using the particular equipment.
In recent years, it has become possible to connect to phone systems certain purchased equipment. However, this too has its problems. For one thing, the phone company has to be notified for an installation of a jack or other suitable means of connection to the internal wiring of the telephone. The phone company installer thereby goes by the phone company's own book. In cases where a discrepancy develops between that book and the specifications of the manufacturer of the particular equipment, the subscriber is frequently left dangling, with the phone company pointing to the manufacturer, and the manufacturer pointing to the phone company. This is also apt to happen if there is some defect in the equipment, with the manufacturer blaming the phone company installer instead.
Against this background of prior-art frustration, various telephone signal pickup devices have enjoyed a certain popularity, until they became frustrated themselves. For instance, inductive pickups have been sold for placement under the telephone, or in a similar position intended to bring about inductive coupling to the telephone ringer coils. Another type of gadget was a suction cup device stuck to the handset for sonic coupling thereto. None of these devices allowed clear recording or high-quality tapping of an audio signal. Major drawbacks were a typically poor coupling and a susceptibility to interference signals.
The death knell for the inductive coupler finally was tolled when the phone company introduced electronic ringing devices that lacked the traditional inductive ringer coils, so that there was nothing for the inductive coupler to pick up.